AbstractClean and ordered chalcopyrite CuInSe2 surfaces are a precondition for the study of the electronic structure by angle-resolved photoelectron spectroscopy. The preparation of welldefined CuInSe2(001) surfaces by the combination of molecular beam epitaxy and a selenium capping and decapping process is described. The surface structure of CuInSe2 epilayers with different bulk composition is compared and analysed by low-energy electron diffraction.Employing near-stoichiometric surfaces, the valence electronic structure of CuInSe2 was investigated by angle-resolved photoelectron spectroscopy at the synchrotron source BESSY 2. This is the first study of the valence band structure of a copper chalcopyrite semiconductor material by photoelectron spectroscopy. The valence band dispersion along τT, i.e. the [001] direction, was investigated by a variation of the excitation energy from 10 to 35 eV under normal emission, and the band dispersion along τT, i.e. the [110] direction, was analysed by angular scans with hv = 13 eV.The valence bands derived from antibonding and bonding Se4p-Cu3d hybrid orbitals, nonbonding Cu3d states and In-Se hybrid states are clearly indentified. The strongest dispersion is found for the topmost valence band with a bandwidth of ∼0.7 eV from τ to T. From τ to N, the observed dispersion was 0.5 eV. The experimental valence bands are discussed in relation to calculated band structures in the literature.
Determination of Conduction and Valence Band Electronic Structure of LaTiO
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